I am new to CNC and just started using a Shapeoko 3. Meshcam seem very promising.

I'm having trouble trying to figure out a simple surfacing pass though. I have a 90mm x90mm block that I want to shave 1.5mm off the top. I'm using a 1" surfacing cutter. The trick is I want it to set it's depth outside the material and then only cut on the X axis. I tried to import a plane the size of the stock and set an oversized margin but that didn't quite work.

Any ideas on how to do this? I could do it with Carbide Create but the box toolpath leaves too many faint lines. X axis only is the cleanest.